Pediatric Brain Tumours/ Chidhood brain tumours

 Symptoms

Brain tumours can cause a multiple symptoms depending on their location, its rate of growth, and the age of the child.

Tumours in any location can cause increased pressure within the skull causing the child to experience headaches, nausea, vomiting, and double vision. In infants, the increased pressure may cause excessive, rapid head growth. Tumours located in the back of the brain (posterior fossa) can also cause unsteadiness and difficulties with speech and swallowing. Tumours located in the top part of the brain (supratentorial) can cause seizures (involuntary convulsions with or without loss of consciousness) or weakness of the arms or legs. Tumours located near the base of the brain (suprasellar) can cause visual problems as well as hormonal imbalances that can lead to several conditions including growth disorders.

Diagnosis

When a child develops symptoms that are suggestive of a brain tumour, the mainstay of establishing the diagnosis is through imaging of the brain. This is done by either a CT scan or MRI Scan. While these types of images will demonstrate whether an abnormal mass is present in the brain, in only a few cases will this be enough to establish what type of a mass it is. Aside from brain tumour, abnormal masses in the brain could be caused by infection, bleeding, or a long-standing congenital abnormality. In most cases, some form of surgery is required in order to remove a sample of tissue. By analyzing the tissue, one can know for sure whether the mass is a tumour and, more importantly, exactly what type of tumour it is.

 Treatment

The treatment of brain tumours varies greatly and is dependent by several factors including the size and location of the tumour, the age of the child, and the expected growth rate of the tumour. The main modalities of treatment are surgery, radiation therapy, and chemotherapy.

 Surgery

Surgery for brain tumours can be performed for different purposes, depending on the type, size and location of the tumour. The possible goals of surgery may be one of or any combination of the following:

1. To remove as much of the tumour as is safely possible. One of the great difficulties in removing brain tumours, as opposed to tumours in other locations in the body, is that extreme care must to be taken to try to prevent harm to the very delicate brain tissue. For most childhood tumours, the prognosis is generally better if the tumour can be either totally or near-totally removed. Therefore, surgery remains the mainstay of therapy for the majority of childhood tumours.

2. To remove enough of the tumour to improve the patient's symptoms. For example, if a large tumour is causing increased pressure in the skull, or weakness of the arms or legs, or seizures, then surgery on the tumour may help relieve these symptoms.

3. To provide a tissue sample of the tumour. This tissue sample is analyzed by pathologists and this will tell the surgeon what type of tumour it is and, possibly, how aggressively it might be expected to behave. This will also help decide what type of treatment is needed.

Radiation Therapy

Radiation therapy involves passing high energy radiation through the body. Radiation slows rapidly growing tissue, like tumours. Radiation therapy is often used in conjunction with surgical therapy. The dose and timing of the radiation regimen depends on the type of tumour. In some cases, radiation might only be applied to the local area of the tumour, whereas in other cases, an additional radiation dose might be given to the entire brain and spinal cord to try to prevent the tumour from seeding via the spinal fluid. Because of the fear that radiation therapy may adversely effect the very young, developing brain, it is usually not performed in infants and very young children. Potential side-effects of radiation therapy include hair loss, nausea, vomiting, fatigue, and local skin irritation.

Chemotherapy

Chemotherapy involves giving very strong medications (directly into the bloodstream or occasionally as pills) that preferentially destroy tumour cells. There are numerous drugs that may be used for various types of brain tumours. Although some chemotherapy drugs can improve the survival of children with certain brain tumours, the drugs themselves can have substantial side-effects, including severe nausea, hair loss, and risk of infection.

 Types of Brain Tumours

There are several different types of brain tumours that can affect children. Only some of the more common ones will be discussed here. 

 Astrocytoma

Astrocytomas are tumours that can either be low-grade or high-grade. The low-grade variety is commonly found in the back of the brain (posterior fossa) and these account for approximately 10% of all childhood brain tumours. They may, however, also be located in the top of the brain (supratentorial). Surgical removal of these tumours, especially in the posterior fossa, carries an excellent prognosis for complete cure.  The overall prognosis for these tumours is very good.

High-grade astrocytomas are most commonly located in the top of the brain (supratentorial). Treatment usually consists of a combination of surgery, chemotherapy, and radiation. These are quite aggressive tumours and the prognosis is much worse than for the low-grade variety.

 Ependymoma

Ependymomas most commonly occur in the back of the brain (posterior fossa). Therapy consists of surgery, attempting to remove as much of the tumour as is safely possible, and radiation therapy. 

 Medulloblastoma

Medulloblastoma is another common tumour of the back of the brain (posterior fossa).Treatment initially consists of surgical removal. This is usually followed by radiation therapy, which frequently involves radiation to the entire brain and spinal cord to prevent the spread of the tumour to another location. Depending on the extent of the tumour, chemotherapy may also be considered.

 Brainstem Glioma

The brainstem is the central area of the brain, where all the nerve fibers that travel between the brain and body meet. Tumours that arise in this delicate location are usually gliomas that can either be high-grade or low-grade 

High-grade brainstem gliomas are very difficult to treat. They may be diagnosed based on brain imaging alone. Surgical removal is extremely difficult and so therapy is usually confined to radiation and, sometimes, chemotherapy.

Low-grade brainstem gliomas are quite different and sometimes need no urgent therapy. They can sometimes simply be watched with repeated brain imaging. It is not uncommon for these to remain unchanged for many years.

Tumours in the brainstem are particularly prone, due to their location, to obstruct the flow of the brain's natural fluid. This causes a build-up of fluid in the brain (hydrocephalus) and increased pressure in the skull. The treatment for this can involve either placement of a silastic tube (shunt) to drain the fluid into the abdomen or the creation of a separate hole in the brain to divert the tumour obstruction (endoscopic third ventriculostomy).

 Craniopharyngioma

These tumours are located near the optic nerves and the pituitary gland, so they frequently cause visual problems and hormonal imbalances. The standard therapy for these tumours is surgery, attempting to remove as much of the tumour as is safely possible. Total removal of the tumour is very difficult and, because of its location, visual disturbances and hormonal imbalances are not uncommon after surgery. Radiation therapy is occasionally used if substantial tumour remains after surgery or if the tumour shows re-growth.